JP2010503540A - Laser processing method and system for different types of targets on workpiece - Google Patents

Abstract

Methods and systems for laser processing different types of targets on a workpiece are provided. This method includes one or more laser output pulses to selectively provide one or more laser output pulses having one or more set pulse widths based on the first type of target being processed. Setting the laser pulse width of the laser pulse. The method further includes determining the pulse shape of the one or more output pulses to selectively provide one or more output pulses having a set pulse shape based on the type of target being processed. Includes steps to set. The method further comprises providing the one or more output pulses having the one or more set pulse widths and a set pulse shape to the at least one target of the first type. Yeah. The method finally includes the one or more laser output pulses to selectively provide one or more laser output pulses having one or more reset pulse widths based on the second type of target being processed. Or resetting the laser pulse width of the laser pulses longer than that.
[Selection] Figure 2

Description

This application claims the benefit of US Provisional Application Serial No. 60 / 844,822, filed September 15, 2006.

1. The present invention relates to laser processing methods and systems for different types of targets on a workpiece.

2. Background Art Laser trimming has been part of the manufacturing process in the semiconductor and microelectronics industries for over 30 years. The industry has derived new link materials and structures with different thin films and structures. One laser processing attempt is to meet the processing needs of all these devices with a single laser trimming system. For example, the processing environment and laser types required for copper processing are not the same as for conventional polycrystalline silicon link processing. Therefore, a laser trimming system designed for processing polycrystalline silicon links has not been able to effectively process copper links.

  Another attempt is that the processing environment and laser type required for blowing or cutting metal links is not the best for conventional thin film trimming. For example, laser trimming systems designed for copper link processing cannot effectively process thin film film resistors. Furthermore, similarly different thin films require different processing conditions. In a laser processing system such as the model M310 which is the product of the assignee of the present application, different laser pulse widths, such as 7 ns and 50 ns pulse widths, are required for various thin film trimming operations. The present assignee's current M310 / M350 system consists of a selected laser having a single desired pulse width. However, the pulse width cannot be easily adjusted or adjusted. This limits the system to narrow product processing with selected pulse widths. Currently, if there are different types of targets or circuit elements that are laser machined with different pulse widths, a complex machining system provides different pulse width lasers that are required. These systems are underutilized due to the mix of products of various target types, reducing the value of the system to customers. A system that processes multiple types of devices with a single laser source adds value to the customer.

  Unless otherwise indicated, the following patents or patent applications assigned to the assignee of the present invention are hereby incorporated by reference in their entirety:

US Patent No. 5,300,756 ('756 patent) “Method For Severing Integrated-Circuit Connection Paths By A Phase-Plate-Adjusted Laser Beam” US Patent No. 5,998,759 ('759 patent) "Laser Precessing" US Patent No. 6,727,458 ('458 patent) "Energy-Efficient, Laser-Based Method And System For Processing Target Material" US Patent No. 6,777,645 ('645 patent) "High-Speed, Precision, Laser-Based Method And System For Processing Material Of One Or More Targets Within A Field" US Patent No. 6,951,995 ('995 patent) "Method And System For High-Speed, Precise Micromachining An Array Of Devices" US Patent No. 6,987,786 ('786 patent) "Controlling Laser Polarization" US Patent Publication No. 2002/0167581 ('7581 published) "Method And Systems For Thermal-Based Laser Processing" US Patent Publication No. 2006/0108337 ('8337 published) "Method And System For Laser Soft Marking" US Patent Publication No. 2004/0188399 ('8339 published) “Energy-Efficient, Laser-Based Method And System For Processing Target Material” US Pat. No. 6,151,338 (not assigned to the assignee of the present invention) discloses a high power laser optical amplification system for material processing.

  One object of the present invention is to provide an improved method and system for laser processing different types of targets on a workpiece.

  In order to achieve the above objects and other objects of the present invention, a method for laser processing different types of targets on a workpiece is provided. This method includes one or more laser output pulses to selectively provide one or more laser output pulses having one or more set pulse widths based on the first type of target being processed. Setting the laser pulse width of the laser pulse. The method further includes determining the pulse shape of the one or more output pulses to selectively provide one or more output pulses having a set pulse shape based on the type of target being processed. Includes steps to set. The method further comprises providing the one or more output pulses having the one or more set pulse widths and a set pulse shape to the at least one target of the first type. Yeah. The method finally includes the one or more laser output pulses to selectively provide one or more laser output pulses having one or more reset pulse widths based on the second type of target being processed. Or resetting the laser pulse width of the laser pulses longer than that.

  The pulse width to be set or reset can be selected from a continuous range of 1 nanosecond to 200 nanoseconds.

  The range may be between 4 nanoseconds and 50 nanoseconds.

  The pulse width may be programmable.

  The output pulse may be supplied by a laser beam supply subsystem. The laser beam may have a flat top profile.

  The set pulse shape may be a square pulse shape.

  The supplied output pulse may have a pulse energy in the range of 0.1 microjoules to 5 microjoules.

  The range may be 0.2 microjoules to 1.5 microjoules.

  The laser pulse may be generated by a pulse shaping laser. The pulse shaped laser may have a repetition rate in the range of 1 kHz to 200 kHz.

  The repetition rate may range from 1 kHz to 50 kHz.

  The output pulse may have a rise time less than 1.5 nanoseconds and a fall time less than 2 nanoseconds.

The output pulse may have a TEM ₀₀ mode.

  The output pulse may have a wavelength in the range of 0.2 microns to 2.5 microns.

  The wavelength may be about 1 micron.

  The wavelength may be about 1.2 microns.

  The wavelength may be about 1.3 microns.

  One of the different types of targets may be a thick film or thin film type device.

  The device may be a circuit element.

  The device may be a thin film resistance element.

  The different types of targets may be links.

  The link may include a metal link.

  The link may include a polysilicon link.

  The metal links may include at least aluminum, gold, and copper links.

  The workpiece may include a semiconductor substrate.

  The target may include a circuit element.

  The circuit element may include a bank of links of a first material and a bank of links of a second material different from the first material.

  The circuit element may include a bank of links and a thick or thin film device.

  The processing may include trimming.

  The trimming may be passive or functional trimming.

  At least one step of the setting may be repeated after all of the same or similar material targets on the workpiece have been processed.

  At least one step of the setting may be repeated during the processing of targets made of different materials on the workpiece.

  In addition, to achieve the above objects and other objects of the present invention, a system is provided for laser processing different types of targets on a workpiece. The system includes a laser subsystem that generates one or more pulses. The system is further operatively connected to the laser subsystem so that the laser pulse width of one or more laser pulses is one or more set pulse widths for the first type of target being processed. A controller configured to selectively provide one or more laser output pulses having: The controller is also operatively connected to the laser subsystem to selectively provide one or more output pulses having a pulse shape set based on the first type of target. Set the pulse shape of one or more output pulses and select one or more laser output pulses with one or more reset pulse widths based on the second type of target to be processed Reconfigure one or more laser pulses to provide automatically. The system further includes a laser beam delivery subsystem having an optical subsystem for delivering the output pulse having the set pulse shape and the pulse width set and reset to the first and second types of targets, respectively. With

  The laser beam supply subsystem may selectively supply the output pulse to the target based on position information.

  The laser subsystem may include a single pulse shape and pulse width adjustable laser.

  The laser subsystem may comprise a fiber laser.

  The laser subsystem may comprise a pulsed laser that rises quickly and descents quickly.

  The laser subsystem may comprise a Q-switched laser.

  The laser subsystem may have a MOPA configuration and may include an oscillator and an amplifier.

  The oscillator may comprise a semiconductor laser whose pulse width is adjustable or adjustable.

  The amplifier may comprise a fiber-based amplifier.

  The laser subsystem may comprise a laser having an output coupler and a laser cavity. The shape and size of the laser cavity may be adjustable, and the reflectivity of the output coupler may be adjustable to set the pulse width.

  The controller may set the pulse width by changing the laser pulse energy level of the laser subsystem.

  The controller may set the pulse width by changing the repetition rate of the laser subsystem.

  The system further includes a sensor subsystem comprising an optical sensor that senses a laser pulse reflected from the workpiece to obtain a signal, and a signal processor that processes the signal to obtain alignment information for laser processing. It may be provided.

  The laser beam may initially be linearly polarized. The system may further comprise an LCVR and an LCVR controller for controlling the LCVR, and the LCVR may controllably rotate the linearly polarized laser beam based on the array of targets.

  The laser beam may have an initial polarization. The system may further include an LCVR and an LCVR controller that controls the LCVR, and the LCVR may controllably change the initial polarization to a desired polarization.

  The optical subsystem may adjust at least one of a spot size and a focal length of a laser beam on the at least one target.

  The system may further comprise a positioning mechanism that provides relative motion between the workpiece and the laser beam.

  In order to further realize the above object and other objects of the present invention, a laser-based material processing method is provided. The method may comprise providing a first target of a first type on a die and providing a second target of a second type on the die. The first and second types are different types. The method further comprises processing the first and second targets with a single pulse shape laser with adjustable pulse width.

  One of the objects of one or more embodiments of the present invention is to provide a laser system / processing method and a system for processing various types of links, including polysilicon, aluminum, gold, copper links on a wafer. That is.

  Another object of one or more embodiments of the present invention is to provide laser processing using a single laser source for a wide variety of processing applications, such as cutting or blowing dissimilar links or trimming thin or thick film resistors on a wafer. It is to provide a method and system.

  One embodiment of the present invention improves the window of the link blowing process by using a pulse shape and pulse width tunable laser, preferably a fiber laser. To achieve this, a fast (<1.5 ns) / fall (<2 ns), pulse-shaped (preferably square) q-switched laser can be used. Also, a MOPA configuration can be used. One choice of MOPA oscillator is a tunable or adjustable pulse width diode laser. One choice of MOPA amplifier is a fiber laser amplifier. Beam shaping optics may be used to generate a flat top beam shape to improve laser processing.

  Faster rise / fall pulsed lasers allow the laser energy to bind well to the material, resulting in more efficient processing. This is particularly noticeable with metal links. The fast descent time avoids the last energy surplus of impact of the typical Q-switch pulse on the material and reduces substrate damage. Furthermore, since the surplus energy in the adjacent area near the trim path is small, the amount of HAZ generated is small. Thus, one or more embodiments of the fast rise / fall pulse shape laser of the present invention are suitable for processing metal links, such as copper or gold links.

  Another aspect of the laser of embodiments of the present invention is the possibility of adjusting the laser pulse duration (pulse width). Different pulse durations can be selected in the laser trimming or processing system to blow or cut the metal link or thin film or thick film circuit element trim, respectively. By flexibly adjusting the pulse duration, the processing window of the metal link blowing or cutting process can be individually optimized, as with the thin or thick film trimming process. Flexible adjustment of the pulse duration can also optimize other laser material processing tasks.

  The pulse width of the proposed laser can be easily adjusted, so the pulse width can be optimized along with other beam characteristics such as pulse energy and beam size to obtain improved processing conditions for thin film and thick film trimming. Can do.

  Spatial beam shaping of the laser beam from a conventional Gaussian to a flat top shape efficiently couples energy and reduces heating in areas adjacent to or along the trim path and underlying substrate. Because energy is efficiently coupled through the trim cut, the generation of HAZ is reduced at the same total energy, and substrate damage is reduced. For this reason, in one or more embodiments of the invention proposed here, a spatially shaped beam, preferably in the form of a flat top beam, is used for trimming or cutting.

  In addition to the shaping pulse, the laser pulse duration can also be easily adjusted. Specific pulse widths can be easily selected for specific thin or thick film materials and structures, thereby eliminating the need to use multiple laser sources in a single material processing system.

  The above features and advantages will be readily apparent when the following detailed description of the best mode is taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic top view of a semiconductor wafer die, partially removed. On the die are thin film resistor elements as well as metal links (ie, copper, gold, aluminum, etc.). Another possible combination of devices to be processed is a thick film device. FIG. 2 is a schematic block diagram of a laser processing system configured in accordance with one embodiment of the present invention. FIG. 3 is a graph of laser material processing pulse output (y-axis) versus time (x-axis) generated in accordance with one embodiment of the present invention. FIG. 4 is a graph of energy processing window (microjoules) versus pulse width showing the dependence of the energy processing window on the laser pulse width in a copper link. Here, the energy processing window (microjoule) is the range of laser pulse energy between the minimum energy required to cut the link and the maximum energy at the dark spot observed under the link. FIG. 5 shows a precision window with a 4 micron spot on the copper link, with half window (microns) of positioning accuracy versus pulse energy (microjoules). This graph shows the change in maximum pulse energy applied to the link as a function of the spot position relative to the center of the link without causing optically observed damage. This half window represents the deviation of the maximum spot position from the link center obtained with each laser pulse energy without observing optical damage. FIG. 6 is a graph of energy processing window (microjoules) versus beam size (microns), where the process window is shown as a function of copper link spot size. This energy processing window (microjoule) is the range of laser pulse energy between the minimum energy required to break the link and the maximum energy at the dark spot observed under the link. FIG. 7 is a graph of energy processing window (microjoules) versus laser pulse width (nanoseconds) showing that the energy processing window is a function of pulse width (for gold links). This energy processing window (microjoule) is the minimum energy required to cut the link and the maximum energy at which dark spots can be observed under the link without producing optically observable damage. The range of laser pulse energy between. FIG. 8 is a pair of graphs, one with 13 ns pulse width and the other with 7 ns pulse width, positioning accuracy half window size (microns) versus pulse energy (microjoules), 4 microns on a gold link. The beam position accuracy window is shown. This graph shows the change in maximum pulse energy applied to the link as a function of the spot position relative to the center of the link without causing optically observed damage. This half window represents the deviation of the maximum spot position from the link center obtained with each laser pulse energy without observing optical damage.

  Referring to FIG. 1, a portion of a semiconductor wafer die is shown having a number of circuit elements formed thereon. The circuit element comprises a bank of 2 micron gold links 10, a bank of 2 micron copper links and a thin film resistor element 14 of SiCr, tantalum nitride or NiCr, both of which are in accordance with the present invention. Can be processed with the method and system of one embodiment.

  Referring to FIG. 2, a laser material processing system constructed in accordance with one embodiment of the present invention is shown. This system comprises the laser subsystem shown in FIGS. 5 and 7 of the aforementioned '458 patent and described in the corresponding portion of the' 458 patent.

  In the preferred embodiment, the laser subsystem comprises a master oscillator and a power amplifier (MOPA) configuration. This system seeds the laser pulse into an amplifier that produces a high power, fast rise time pulse. Seed lasers have fast rise times and short pulse widths at very low energy levels. Laser amplifiers generate enough energy to perform material processing. In FIG. 2, both the seed laser and the laser amplifier are referred to as a fiber laser.

  Fiber laser amplifiers and fast infrared laser diodes with output wavelengths suitable for laser processing applications are preferred. This fiber laser system produces a laser pulse with a preferred shape and speed as shown in FIG. 3, ie, a fast rise time of the pulse, a flat top, and a fast fall time. This pulse shape then derives the desired laser material interaction results as a result of reduced metal reflectivity and reduced energy diffusion into the device.

  Preferably, the laser pulse width is easily settable and may be programmable. One such example is a fiber laser from IPG Photonics that is used in certain M430 memory repair systems by the assignee of the present invention. The laser pulse width can be selected over a continuous range of 4 ns to 20 ns.

  US Patent Application Publication No. 2004/0188399, assigned to the assignee of the present invention, discloses various embodiments of laser systems used to form or remove surface structures. For example, a MOPA system having an optical fiber amplifier is disclosed. The laser processing system includes an output subsystem having an A-O modulator. The MOPA and power modulator selectively directs one or more laser pulses to the target material based on the position information. Each output pulse incident on the surface has a different pulse width.

  Another way to set the pulse width is to adjust the shape and dimensions of the laser cavity along with the reflectivity of the output coupler. The laser pulse width is changed by changing the cavity length and the reflectivity of the output coupler. The distortion of both cavity mirrors (total reflector and output coupler) will also change if the total cavity length changes according to the laser resonant structure. The theory and operation of laser resonators can be found in many textbooks, handbooks, and laser manufacturer catalogs. One such document is “Laser” by Peter Miloni and Joseph Everber, published in 1988 by John Wiler & Sons. Chapter 14 “Laser Resonators” explains in detail the theory and principles of laser cavities.

  Another method of setting the pulse width takes advantage of the variable laser characteristics, that is, the pulse width decreases as the laser energy increases. The laser can be driven at a high pulse energy level to obtain the required pulse width, and then the beam is attenuated externally to obtain the required energy density.

  To set or reset the pulse width, other variable laser characteristics, i.e., increasing the pulse width with the repetition rate of the laser, may be utilized.

  Referring again to FIG. 2, a laser diode having a rise time of nanoseconds or less in response to a modulating drive waveform is the starting point of the fiber laser MOPA structure, and this laser diode serves as a seed leather. Laser diodes typically have multiple longitudinal modes, and subsystems are configured with single mode operation or otherwise with a large component in power, or with an integrated fiber grating in the system. May be.

  The system of FIG. 2 also includes a lens (not shown) that collimates the fiber output, a conventional shutter, a depolarizer, a polarizer, an insulator (prevents back reflection), a mirror, a beam splitter, and a relay. It includes a lens, an AOM (acousto optic modulator), and a pre-expander, all of which are well known in the art and are disclosed in numerous patents describing fiber lasers.

  The system of FIG. 2 also includes an optical AC voltage controlled liquid crystal variable retarder (LCVR) and a mount. The LCVR comprises a birefringent liquid crystal sandwiched between two plates. As is known in the art, birefringent liquid crystals can rotate the polarization of a laser beam because light travels at different speeds along different axes in a birefringent liquid crystal, resulting in a phase shift in polarization. . Here, since the LCVR rotates the linearly polarized beam, it is possible to obtain an arbitrary linearly polarized beam on a target (link) having a polarization parallel or orthogonal to the length direction of the link. In addition, birefringent liquid crystals can also convert linearly polarized laser input into elliptical or circularly polarized laser output. As the laser beam moves from the LCVR to the work surface of the die being processed, it maintains its polarization.

  The voltage applied to the liquid crystal variable retarder is controlled by a digital controller and / or a manual controller that interfaces the liquid crystal variable retarder through a cable. The manual controller can be adjusted by the user to change the LCVR voltage based on the user's knowledge, for example, whether the link to be machined or blown is vertical or horizontal. The digital controller receives the input from the computer and automatically changes the voltage of the LCVR based on the information about the arrangement of links to be cut stored in the computer. The input from this computer controls the digital controller and the voltage applied to the LCVR is appropriate. Lateral polarization, longitudinal polarization, circular polarization, etc. can be determined by experience.

  In one or more embodiments, the digital controller is programmed to select from three different voltages corresponding to vertical linear polarization, horizontal linear polarization, and circular polarization. In other embodiments, the digital controller stores different voltages, which may include voltages corresponding to various elliptical polarizations. Other embodiments are possible, and any liquid crystal variable retarder can convert linearly polarized light vertically or horizontally where such angled polarization proves useful for cutting or trimming certain types of structures. You may rotate to various angles other than.

  The system of FIG. 2 may also include a subsystem that provides a focused beam to a single die target on a semiconductor wafer. The laser beam positioning mechanism preferably includes a pair of mirrors and a galvanometer attached to each of them (various available from the assignee of the present application). The beam positioning mechanism directs the laser beam through a lens (telecentric or non-telecentric). Preferably, the lens has a scanning area of at least 10 mm x 10 mm and produces a spot of 6 microns or less at a working distance of at least 40 mm for access to contact with the probe. More preferably, the laser spot size is in the range of 4 to 5 microns.

  The XY galvanometer mirror system achieves an angle reach on the entire wafer when sufficient dimensions and accuracy are ensured. Otherwise, various positioning mechanisms may be used to provide relative motion between the wafer and the laser beam. For example, a two-axis aiming step and a repeat translator may be used to position the wafer galvanometer based on the mirror system (eg, in the XY plane). The laser beam positioning mechanism moves the two long orthogonal axes of the laser beam, thereby realizing two-dimensional positioning of the laser beam over the entire wafer area. Each mirror and associated galvanometer moves the beam along the x or y axis, respectively, under computer control.

  The beam positioning subsystem may comprise other optical components, such as a computer controlled optical subsystem that adjusts the laser spot size and / or automatically aims the laser spot at a location on the wafer die.

  The system of FIG. 2 may also comprise an optical sensor system in the alignment process. In one embodiment, the optical sensor of the system comprises a camera (disclosed in the '995 patent) that operates in combination with a pair of illuminators as shown in FIG. In another embodiment, the optical sensor of the system comprises a single photodetector, where the laser pulse is attenuated by the AOM and sensed by the photodetector after the attenuated pulse is reflected back from the die. This reflection is from the alignment structure or other structures used for alignment. The preferred alignment structure width is 0.5x to 2x the spot diameter, more preferably equal to the spot size.

  The reflection may be from a non-aligned structure. For example, the reflection is from the link or group of links being processed, and the reflection is used to detect whether the edge of the link is precisely aligned with the group of links to be processed. In yet another embodiment, a low power laser (not shown in FIG. 2, but illustrated in FIG. 13 of the '7581 publication and described in the relevant specification) is used for optical inspection or detection purposes. May be.

  A semiconductor wafer comprising a die having copper links is processed by cutting the links with the laser material processing system of FIG. The copper link has a width of 2 μm and a pitch of 22 μm. The processing system includes a fiber laser that produces a shaped pulse with adjustable pulse width, in this example a square pulse. The target spot size is about 4 μm. Die reference marks near the banks of each link (ie, 28 links per bank) are used to verify that the aiming plane height is correct before linking or blasting.

  The link is processed using 7 ns, 13 ns, 16 ns, and 21 ns wide pulses. All links are processed with link-wide polarization, which gives the best results with respect to the process window.

Results The following table summarizes the clean blow and darkening thresholds.

  In the processing of copper links, it is clear that the pulse shape is as important to the best processing window as the pulse width. In other words, the processing window depends on both the pulse width and the pulse shape.

  The graph of FIG. 4 shows the dependence of the energy processing window on the laser pulse width in the copper link.

  In the positioning accuracy test, the beam center is intentionally moved away from the link center, and damage is determined using the same damage condition that is optically observed damage. The graph of FIG. 5 is a 4 μm spot size beam positioning window of a copper link wafer using an IPG laser.

  Since the link is 2 μm wide, a 6 μm beam has little processing window because damage always occurs before the link is blown cleanly. The processing window becomes maximum when the beam size is about 4 μm as shown in the graph of FIG. In this graph, a 2 μm wide copper link was processed using a 13 ns pulse width IPG laser.

  Similarly, gold link wafers were processed with the system of FIG. The gold links are 2 μm wide and have a 16.5 μm pitch. The trimming system comprises a fiber laser that produces a shaped pulse with adjustable pulse width, in this example a square pulse. The target spot size is about 4 μm. Die reference marks near the banks of each link (ie, 40 links per bank) are used to verify that the aiming plane height is correct before blasting the links.

  The link is processed using 7 ns, 13 ns, 16 ns, and 21 ns wide pulses. All links are processed with link-wide polarization, which gives the best results with respect to the process window.

Results The following table summarizes the clean blow and darkening thresholds.

  In the processing of gold links, it is clear that the pulse shape is as important for the best processing window as the pulse width. In other words, the processing window depends on both the pulse width and the pulse shape.

  The graph of FIG. 7 shows the dependence of the energy processing window on the laser pulse width in the gold link.

  The positioning accuracy test shown in FIGS. 5 and 8 is performed by intentionally offsetting the beam center from the link center and visually observing the damage of each link. Each graph shows the position offset relative to the observed damage energy threshold. The maximum energy value corresponds to a near-ideal spot-to-link alignment. The energy processing window reflects the positioning error of the processing system and is usually below the maximum energy in FIGS. The graphs of FIGS. 5 and 8 show a 4 μm spot size beam positioning window of a wafer using a copper or gold link using an IPG laser. The test described above is the same as the name “Link Cutting Making” of the Veneer run test described in Chapter 19 of “LIA HANDBOOK OF LASER MATERIALS PROCESSING” (particularly, FIG. 11 of the chapter).

  The spot size of the beam affects the processing window of the gold link as well as the copper link.

  An IPG fiber laser may be used in one embodiment of the system of the present invention to generate an adjustable pulse width from 5 ns to 21 ns. As shown in FIG. 3, the duration can be extended to 50 ns or more, for example, 200 ns, or can be shortened to 1 ns.

  In another embodiment of the system, a 1.3 micron fiber laser (erbium doped amplifier and 1.3 micron laser diode) is used to take advantage of the wavelength-sensitive transmissive property of a silicon substrate. Well, the processing window is further improved when combined with square pulses and selectable pulse widths.

General laser processing conditions:
(A) Metal link blowing 2 μm wide copper link: pulse width 13-16 ns, processing energy 1 μj-4 μj
2 μm wide gold link: pulse width 7-16 ns, processing energy 0.2-4.2 μj
(B) Trimming of thin film resistor SiCr: Usually a short pulse is effective -7-13 ns, energy 0.05-0.5 μj
NiCr: Usually a long pulse is effective-25-50 ns, energy 0.1-0.5 μj
Tantalum nitride: 25-50 ns, 0.1-0.5 μj
(C) Thick film resistor trimming Pulse width 7-50 ns, 1-40 μj

  A single pulse shaping and pulse width tunable laser in a laser processing system can be provided and used for link blowing as well as thin film and thick film resistor trimming.

  The pulse energy of the pulse of the pulse shaping laser may be 0.1 μj to 100 μj, typically 20-40 μj.

  The pulse repetition rate of the pulse shaping laser may be 1 KHz to 200 KHz, typically 1 to 50 KHz.

  The pulse rise time of the pulse shaping laser may be less than 1.5 ns and the fall time may be less than 2 ns.

  The pulse of the pulse shaping laser may be a square pulse.

  The adjustable or adjustable pulse width (duration) of the pulse shaping laser may be 1 ns to 200 ns, typically 4 ns to 50 ns.

  The pulse of the pulse shaping laser may have a TEM00 beam.

  The pulse shaping laser may use a MOPA configuration. The seeder can be either a semiconductor laser or a Q-switched laser and the amplifier can be a fiber laser.

  The pulse shaping laser may be a fiber laser.

  The pulse wavelength of the pulse shaping laser may be 0.2 μm to 2.5 μm. For example, a green wavelength (532 nm) or a purple wavelength (355 nm) obtained by shifting the output wavelength of the IR approximate fiber laser amplifier.

  The wavelength of the pulse of the pulse shaping laser may be about 1 μm, for example 1.064 microns.

  The pulse wavelength of the pulse shaping laser may be 1.2 μm.

  The pulse wavelength of the pulse shaping laser may be 1.3 μm.

  One such laser is a conventional fiber laser from IPG that is used in the assignee's memory repair system of the present invention. A plurality of narrowly spaced pulses are generated in a rapid succession and are used in certain embodiments, such as before measurement.

The method and system of one embodiment of the present invention can handle the following:
A thin film resistor of SiCr, NiCr base or tantalum nitride formed on a die of a semiconductor wafer; and
Link fuses such as polysilicon, copper, aluminum, or gold link fuses

  In one embodiment, all targets of the same or similar material on all dies on the wafer are processed before changing the pulse width and / or shape. In another example, the pulse width and / or shape may be changed during processing of different materials on a single die.

  In one embodiment, passive or functional trimming may be performed.

  While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is to be understood that various modifications can be made without departing from the purpose and scope of the invention.

Claims (50)

In a method of laser processing different types of targets on a workpiece, the method comprises:
A laser of one or more laser pulses to selectively provide one or more laser output pulses having one or more set pulse widths based on the first type of target being processed. Setting the pulse width; and
Setting the pulse shape of the one or more output pulses to selectively provide one or more output pulses having a set pulse shape based on the type of target being processed;
Supplying the one or more output pulses having the one or more set pulse widths and a set pulse shape to at least one target of the first type;
The one or more laser pulses to selectively provide one or more laser output pulses having one or more reset pulse widths based on the second type of target being processed. Resetting the laser pulse width of the method.   2. The method according to claim 1, wherein the set or reset pulse width is selectable from a continuous range of 1 nanosecond to 200 nanoseconds.   The method of claim 2, wherein the range is between 4 nanoseconds and 50 nanoseconds.   The method of claim 1, wherein the pulse width is programmable.   The method of claim 1, wherein the output pulse is provided by a laser beam delivery subsystem and the laser beam has a flat top profile.   The method according to claim 1, wherein the set pulse shape is a square pulse shape.   2. The method of claim 1, wherein the pulse energy of the supplied output pulse is in the range of 0.1 microjoules to 5 microjoules.   8. The method of claim 7, wherein the range is 0.2 microjoules to 1.5 microjoules.   2. The method of claim 1, wherein the laser pulse is generated by a pulse shaping laser and the repetition rate of the pulse shaping laser is in the range of 1 kHz to 200 kHz.   10. The method of claim 9, wherein the repetition rate is in the range of 1 kHz to 50 kHz.   The method of claim 1, wherein one of the different types of targets is a thick film or thin film device.   12. The method of claim 11, wherein the device is a thin film resistor element.   13. The method according to claim 12, wherein at least a part of the thin film resistor element is made of one or more of SiCr, NiCr base, and tantalum nitride material.   The method of claim 1, wherein the different types of targets are links.   15. The method of claim 14, wherein the link comprises one or more of polysilicon, aluminum, gold, and copper links.   2. The method of claim 1, wherein the target includes a bank of links of a first material and a bank of links of a second material different from the first material. how to.   The method of claim 1, wherein the target comprises a bank of links and a thick or thin film type device.   The method of claim 1, wherein the processing includes trimming.   The method of claim 18, wherein the trimming is passive or functional trimming.   The method of claim 1, wherein at least one of the steps in the setting is repeated after all of the same or similar material targets on the workpiece have been processed.   The method of claim 1, wherein at least one of the steps in the setting is repeated during processing of a target made of different materials on the workpiece.   2. The method according to claim 1, wherein the processing includes trimming and link blowing, and the step of setting and resetting the laser pulse width individually sets the processing window of the link blowing as well as the trimming. A method characterized in that it can be optimized.   The method of claim 1, wherein the spot size of at least one target is in the range of 4 microns to 5 microns and has a working distance of 40 mm and an area of at least 10 mm multiplied by 10 mm. In a laser-based material processing method,
Providing a first target of a first type on a die;
Providing a second type of second target on the die, wherein the first and second types are different types;
Treating the first and second targets with a single pulse-shaped laser with adjustable pulse width. A method for blowing and trimming thin film resistor links on a workpiece, the method comprising:
To selectively provide one or more laser output pulses of a first pulse width of 13-16 ns or a second pulse width of 7-16 ns, respectively, based on the copper or gold link being blown. Setting the laser pulse width of one or more laser pulses, wherein the processing energy of the one or more output pulses to the copper or gold is 1 μj-4 μj and 0.2-4.2 μj, respectively. A step and
Setting the pulse shape of the one or more output pulses to selectively provide the one or more output pulses based on the type of target being lasered;
Supplying at least a portion of the one or more output pulses of the first or second set pulse width in the set pulse shape to the copper or gold link, respectively;
One or more laser outputs having either a third pulse width of 7-13 ns or a fourth pulse width of 25-50 ns, respectively, based on either a SiCr thin film resistor or a NiCr or tantalum nitride thin film resistor Resetting the laser pulse width of one or more laser pulses to selectively provide pulses, wherein the processing energy of one or more output pulses for the thin film resistor is 0.05 respectively A step that is -05 [mu] j or 0.1-0.5 [mu] j. A system for laser processing different types of targets on a workpiece, the system comprising:
A laser subsystem for generating one or more pulses;
A controller operatively connected to the laser subsystem;
A pulse of one or more laser pulses to selectively provide one or more laser output pulses having one or more set pulse widths based on the first type of target being processed. Set the width,
Setting the pulse shape of one or more output pulses to selectively provide one or more output pulses having a set pulse shape based on the first type of target;
Based on the second type of target being processed, the one or more laser pulses are selectively provided to selectively provide one or more laser output pulses having one or more reset pulse widths. The controller to reconfigure,
A laser beam supply subsystem having an optical subsystem for supplying at least a part of the output pulse having the set pulse shape and the pulse width set and reset to the first and second types of targets, respectively; The system characterized by comprising.   27. The system of claim 26, wherein the rise time of the output pulse is less than 1.5 nanoseconds and the fall time is less than 2 nanoseconds.   27. The system according to claim 26, wherein the wavelength of the output pulse is in the range of 0.2 microns to 2.5 microns.   30. The system of claim 28, wherein the wavelength is one of about 1 micron, about 1.2 microns, about 1.3 microns, about 0.532 microns, and about 0.355 microns. Feature system.   27. The system of claim 26, wherein the laser beam delivery subsystem selectively delivers the output pulse to the target based on position information.   27. The system of claim 26, wherein the laser subsystem includes a single pulse shape and pulse width tunable laser.   27. The system of claim 26, wherein the laser subsystem comprises a fiber laser.   27. The system of claim 26, wherein the laser subsystem comprises a pulse-shaped laser that rises quickly and descents quickly.   34. The system of claim 33, wherein the laser subsystem comprises a Q-switched laser.   27. The system of claim 26, wherein the laser subsystem has a MOPA configuration and includes an oscillator and an amplifier.   36. The system of claim 35, wherein the oscillator comprises a semiconductor laser whose pulse width is adjustable or adjustable.   36. The system of claim 35, wherein the amplifier comprises a fiber-based amplifier.   27. The system of claim 26, wherein the laser subsystem comprises a laser having an output coupler and a laser cavity, the shape and dimensions of the laser cavity are adjusted to set the pulse width, and the output coupler A system characterized in that the reflectivity is adjusted.   27. The system of claim 26, wherein the controller sets the pulse width by changing a pulse energy level of a laser of the laser subsystem.   27. The system of claim 26, wherein the controller sets the pulse width by changing a laser repetition rate of the laser subsystem.   27. The system of claim 26, further comprising: an optical sensor that senses a laser pulse reflected from the workpiece to obtain a signal; and a signal processor that processes the signal to obtain laser processing alignment information. A system comprising a sensor subsystem comprising:   42. The system of claim 41, wherein the laser pulse is reflected from the alignment structure of the workpiece, the alignment structure having a width that is 1/2 to 2 times the diameter of a laser spot supplied to the target. A system characterized by that.   43. The system of claim 42, wherein the width of the alignment structure is substantially equal to a spot diameter.   42. The system of claim 41, wherein the laser pulse is reflected from one link in a group of links to be laser processed.   27. The system of claim 26, wherein the laser beam is initially linearly polarized and the system further comprises an LCVR and an LCVR controller that controls the LCVR, wherein the LCVR is the linearly polarized laser. A system that controlslably rotates a beam based on the array of targets.   27. The system of claim 26, wherein the laser beam has an initial polarization and the system further comprises an LCVR and an LCVR controller that controls the LCVR, wherein the LCVR converts the initial polarization to a desired polarization. A system characterized by controllable change.   27. The system of claim 26, wherein the optical subsystem adjusts at least one of a spot size and a focal length of a laser beam on the at least one target.   27. The system of claim 26, further comprising a positioning mechanism that provides relative motion between the workpiece and the laser beam.   27. The system of claim 26, wherein the system has a positioning accuracy half window of less than 0.6 microns. A system for laser processing different types of targets on a workpiece, the system comprising:
A laser subsystem having a single tunable or adjustable pulse width semiconductor laser and a fiber-based amplifier for generating one or more laser pulses;
A controller operatively connected to the laser subsystem;
A pulse of one or more laser pulses to selectively provide one or more laser output pulses having one or more set pulse widths based on the first type of target being processed. Set the width,
Setting the pulse shape of one or more output pulses to selectively provide one or more output pulses having a set pulse shape based on the first type of target;
Based on the second type of target being processed, the one or more laser pulses are selectively provided to selectively provide one or more laser output pulses having one or more reset pulse widths. The controller to reconfigure,
A lens for supplying at least a part of the output pulse having the set pulse shape and the pulse width set and reset for each of the first and second types of targets based on position information; A laser beam delivery subsystem comprising an optical subsystem, wherein the optical subsystem adjusts at least one of spot size and aiming distance on at least one target, and the lens has a scanning area of at least 10 mm x 10 mm A laser beam delivery subsystem that produces a spot of 6 microns or less at a working distance of at least 40 mm for access to contact with the probe;
A sensor subsystem having an optical sensor for sensing a laser pulse reflected from the workpiece to obtain a signal;
A signal processor for processing the signal to obtain laser processing alignment information;
LCVR for optically processing the laser beam;
An LCVR controller for controlling the LCVR;
A positioning mechanism that achieves relative movement between the workpiece and the laser beam;
A system characterized by comprising.

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